Cooler for optics transmitting high intensity light

ABSTRACT

Systems provide cooling of an optic such as an optically addressed light valve such that the valve is sensitive to temperature and pressure variations and is thus temperature and pressure controlled. In the case of an optic such as an optically addressed light valve, the fluid pressure outside the valve is low enough that it does not compress the liquid crystal gap of the valve. The cooling fluid is transparent to the high powered wavelength of light used during operation such as in an additive manufacturing process.

STATEMENT AS TO RIGHTS TO APPLICATIONS MADE UNDER FEDERALLY SPONSOREDRESEARCH AND DEVELOPMENT

The United States Government has rights in this application pursuant toContract No. DE-AC52-07NA27344 between the United States Department ofEnergy and Lawrence Livermore National Security, LLC for the operationof Lawrence Livermore National Laboratory.

BACKGROUND

Field of Endeavor

The present application relates to the thermal management of optics, inparticular light valves and more particularly to a cooler for continuouslight valve operation in additive manufacturing

State of Technology

This section provides background information related to the presentdisclosure which is not necessarily prior art.

U.S. Pat. No. 4,944,817 for multiple material systems for selective beamsintering issued Jul. 31, 1990 to David L. Bourell et al and assigned toBoard of Regents, The University of Texas System provides the state oftechnology information reproduced below.

A method and apparatus for selectively sintering a layer of powder toproduce a part comprising a plurality of sintered layers. The apparatusincludes a computer controlling a laser to direct the laser energy ontothe powder to produce a sintered mass. The computer either determines oris programmed with the boundaries of the desired cross-sectional regionsof the part. For each cross-section, the aim of the laser beam isscanned over a layer of powder and the beam is switched on to sinteronly the powder within the boundaries of the cross-section. Powder isapplied and successive layers sintered until a completed part is formed.

U.S. Pat. No. 5,155,324 for a method for selective laser sintering withlayerwise cross-scanning issued Oct. 12, 1992 to Carl R, Deckard et al,University of Texas at Austin, provides the state of technologyinformation reproduced below.

Selective laser sintering is a relatively new method for producing partsand other freeform solid articles in a layer-by-layer fashion. Thismethod forms such articles by the mechanism of sintering, which refersto a process by which particulates are made to form a solid mass throughthe application of external energy. According to selective lasersintering, the external energy is focused and controlled by controllingthe laser to sinter selected locations of a heat-fusible powder. Byperforming this process in layer-by-layer fashion, complex parts andfreeform solid articles which cannot be fabricated easily (if at all) bysubtractive methods such as machining can be quickly and accuratelyfabricated. Accordingly, this method is particularly beneficial in theproduction of prototype parts, and is particularly useful in thecustomized manufacture of such parts and articles in a unified mannerdirectly from computer-aided-design (CAD) orcomputer-aided-manufacturing (CAM) data bases.

Selective laser sintering is performed by depositing a layer of aheat-fusible powder onto a target surface; examples of the types ofpowders include metal powders, polymer powders such as wax that can besubsequently used in investment casting, ceramic powders, and plasticssuch as ABS plastic, polyvinyl chloride (PVC), polycarbonate and otherpolymers. Portions of the layer of powder corresponding to across-sectional layer of the part to be produced are exposed to afocused and directionally controlled energy beam, such as generated by alaser having its direction controlled by mirrors, under the control of acomputer. The portions of the powder exposed to the laser energy aresintered into a solid mass in the manner described hereinabove. Afterthe selected portions of the layer have been so sintered or bonded,another layer of powder is placed over the layer previously selectivelysintered, and the energy beam is directed to sinter portions of the newlayer according to the next cross-sectional layer of the part to beproduced. The sintering of each layer not only forms a solid mass withinthe layer, but also sinters each layer to previously sintered powderunderlying the newly sintered portion. In this manner, the selectivelaser sintering method builds a part in layer-wise fashion, withflexibility, accuracy, and speed of fabrication superior to conventionalmachining methods.

SUMMARY

Features and advantages of the disclosed apparatus, systems, and methodswill become apparent from the following description. Applicant isproviding this description, which includes drawings and examples ofspecific embodiments, to give a broad representation of the apparatus,systems, and methods. Various changes and modifications within thespirit and scope of the application will become apparent to thoseskilled in the art from this description and by practice of theapparatus, systems, and methods. The scope of the apparatus, systems,and methods is not intended to be limited to the particular formsdisclosed and the application covers all modifications, equivalents, andalternatives falling within the spirit and scope of the apparatus,systems, and methods as defined by the claims.

When operating an Optically Addressed Light Valve (OALV) continuously ina diode additive manufacturing process with enough diode light to meltmost metals, excessive optical absorption levels in the valve can beginto have significant thermal effects. The inventors have developedapparatus, systems, and methods to prevent the valve from overheatingand leading to non-operation.

The inventors' apparatus, systems, and methods provide cooling of anoptically addressed light valve such that the valve is temperaturecontrolled. The fluid pressure outside the valve is low enough that itdoes not compress the liquid crystal gap. The cooling fluid istransparent to the high powered wavelength of light used in the printingprocess.

The apparatus, systems, and methods are susceptible to modifications andalternative forms. Specific embodiments are shown by way of example. Itis to be understood that the apparatus, systems, and methods are notlimited to the particular forms disclosed. The apparatus, systems, andmethods cover all modifications, equivalents, and alternatives fallingwithin the spirit and scope of the application as defined by the claims.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are incorporated into and constitute apart of the specification, illustrate specific embodiments of theapparatus, systems, and methods and, together with the generaldescription given above, and the detailed description of the specificembodiments, serve to explain the principles of the apparatus, systems,and methods.

FIG. 1 illustrates one embodiment of the inventor's apparatus, systems,and methods.

FIG. 2 shows the light valve cooling system in greater detail.

FIG. 3 illustrates a circulation system for cooling the light valve.

DETAILED DESCRIPTION OF SPECIFIC EMBODIMENTS

Referring to the drawings, to the following detailed description, and toincorporated materials, detailed information about the apparatus,systems, and methods is provided including the description of specificembodiments. The detailed description serves to explain the principlesof the apparatus, systems, and methods. The apparatus, systems, andmethods are susceptible to modifications and alternative forms. Theapplication is not limited to the particular forms disclosed. Theapplication covers all modifications, equivalents, and alternativesfalling within the spirit and scope of the apparatus, systems, andmethods as defined by the claims.

Additive manufacturing, or 3D printing, is the process of turningdigital designs into three-dimensional objects. It is a convenient andaffordable way to make prototypes as well as finished products, makingit popular with businesses, hobbyists and inventors. One of thetechnologies is Powder Bed Fusion (PBF) which includes the Direct MetalLaser Sintering (DMLS), Electron Beam Melting (EBM), Selective HeatSintering (SHS), Selective Laser Melting (SLM) and Selective LaserSintering (SLS). Powder bed fusion (PBF) system uses a laser or electronbeam to melt and fuse material powder together. Electron beam melting(EBM), methods require a vacuum but can be used with metals and alloysin the creation of functional parts. The Powder Bed Fusion processesinvolve the spreading of the powder material over previous layers.

Referring now to the drawings embodiments of the inventor's apparatus,systems, and methods is illustrated that provides an optically addressedlight valve (OALV) such that the valve is temperature controlled, thefluid pressure outside the valve is low enough that it does not compressthe liquid crystal gap internal to the OALV, and that the cooling fluidis transparent to the high powered wavelength of light used in theprinting process. This embodiment is designated generally by thereference numeral 100. The system 100 produces a final product asdescribed below.

Initially a 3D model of the desired product is designed by any suitablemethod, e.g., by bit mapping or by computer aided design (CAD) softwareat a PC/controller. The CAD model of the desired product iselectronically sliced into series of 2-dimensional data files, i.e. 2Dlayers, each defining a planar cross section through the model of thedesired product. The 2-dimensional data files are stored in a computerand provide a digital image of the final product.

The digital images are used in the additive manufacturing system toproduce the final product. Powder particles are applied to a substratein a layer by layer process, melted and allowed to re-solidify toproduce the final product. The digital image of the first 2D layer isused to produce the first layer of the desired product. The digitalimage of the first 2D layer is used to create a mask that only allowsthe desired portion of the laser beam to pass through the opticallyaddressed light valve (OALV) system.

The OALV system, or Light Valve System is composed of a number ofelements such as the OALV itself, a patterned light generating sourcesuch as a digital light projector (DLP) emitting a wavelength of lighttuned to the absorption band of the semiconductor component of the OALV,and a polarizer mirror for splitting the light exiting the OALV andrejecting the polarization state of the light not desired, allowing thedesired portion to continue on to the powder layer on the substrate.

Referring now to FIG. 1 a first embodiment of the inventor's apparatus,systems, and methods, and how they can be used in a larger additivemanufacturing system is illustrated. This embodiment is designatedgenerally by the reference numeral 100. The embodiment 100 includes thecomponents listed and described below.

-   -   Computer controller 102.    -   Mask information portion 104.    -   Build material supply 106.    -   Delivery system 108.    -   Light source 110.    -   Light valve system 112.    -   Light valve cooling system 114.    -   Substrate 116.    -   First layer of metal powder particles 118.    -   Light valve system component 120.    -   Projected beam 124.

As illustrated in FIG. 1, a computer controller 102 is used to performthe various operations of the system 100. A delivery system 108 directsmetal powder particles from a material build supply 106 onto a substrate116. A light source emits a projected beam 124 which is later directedonto the layer 118 of metal powder particles that have been deposited onthe substrate 116. The digital image of the first 2D layer that has beenstored in the mask information 104 portion of the computer controller102 is used to produce the first layer 118 of the desired product.

The mask information 104 is directed to the light valve system 112. Thelight source 110 produces a light beam 120 which upon interaction withthe light valve system 112 is split into two components. The component120 represents the un-altered full laser beam emitted from the lightsource 110, the component 124 represents the portion of the lightcontaining the digital image of the first 2D layer. The component whichrepresents the portion of the light beam that is outside of the digitalimage of the first 2D layer is rejected from the system at this point,typically through a beam dump within the light valve system 112. Thelight valve system 112 acts as a dynamic mask and allows the portion 124containing the digital image of the first 2D layer to pass whilerejecting the component that is outside of the digital image of thefirst 2D layer.

The projected beam 124 containing the digital image of the first 2Dlayer is projected from the light valve system 112 onto the layer 118 ofmetal powder particles that has been deposited on the substrate 116. Theprojected beam 124 solidifies the metal powder particles according tothe digital image of the first 2D layer information producing thefinished first layer 118. Once the first layer 118 is completedproduction of the second layer of the product is started. A second layerof metal powder particles is applied on top of the competed first layer118. This procedure is continued by repeating the steps and building thefinal product in a layer by layer process.

The light valve system 112 is temperature controlled by a light valvecooling system 114. The light valve cooling system 114 uses a coolingfluid that is transparent to the wavelength of light in the high poweredbeam from the light source 110 used in the printing process.

When operating the light valve system 112 continuously in the additivemanufacturing process with enough light energy to melt most metals, thesmall absorption levels in the light valve system 112 begin to havesignificant thermal effects. Absorption, if any, is typically due tohigher than expected impurity levels in the OALV transparent glass orcrystal components. If impurities are too high, excessive absorption ofthe light source 110 have been seen to occur, which can lead tooverheating and non-operation. To prevent the light valve system 112from overheating and leading to non-operation, significant coolingstrategies must be implemented.

Referring to FIG. 2, the light valve cooling system 114 is shown ingreater detail. A cross section 200 of the light valve cooling system114 illustrates the circulation of a cooling fluid over the light valve112. The light valve 114 and the light valve cooling system 200 includesa first light valve cooling housing body part 202, a second light valvecooling housing body part 204, windows 206, coolant inlet ports 208,coolant outlet ports 210, light valve center housing part 212, and lightvalve 214.

A supply line 218 from a coolant supply/heat exchanger directs coolingfluid into the light valve cooling system 114. A return line 220 directsthe cooling fluid from the light valve cooling system 114 back into thecoolant supply/heat exchanger. The arrows 216 show the flow of thecooling fluid through the light valve cooling system 114.

Referring to FIG. 3, a circulation system for cooling the light valve112 is illustrated. The light valve system 112 operates with enoughlight energy to melt most metals and the small absorption levels in thelight valve system 112 begin to have significant thermal effects. Toprevent the light valve system 112 from overheating a cooling fluidcirculation system 300 circulates a fluid for cooling the light valveinside the light valve housing 302.

The cooling fluid circulation system 300 includes a heat exchanger 304,a coolant supply 306, a pump 308, a supply line 310, and a return line312. The supply line 310 from the coolant supply 306 directs the coolingfluid into the light valve housing 302. The return line 312 directs thecooling fluid from the light valve 302 into the heat exchanger 304. Theheat exchanger 304 is part of the coolant supply.

Although the description above contains many details and specifics,these should not be construed as limiting the scope of the applicationbut as merely providing illustrations of some of the presently preferredembodiments of the apparatus, systems, and methods. Otherimplementations, enhancements and variations can be made based on whatis described and illustrated in this patent document. The features ofthe embodiments described herein may be combined in all possiblecombinations of methods, apparatus, modules, systems, and computerprogram products. Certain features that are described in this patentdocument in the context of separate embodiments can also be implementedin combination in a single embodiment. Conversely, various features thatare described in the context of a single embodiment can also beimplemented in multiple embodiments separately or in any suitablesubcombination. Moreover, although features may be described above asacting in certain combinations and even initially claimed as such, oneor more features from a claimed combination can in some cases be excisedfrom the combination, and the claimed combination may be directed to asubcombination or variation of a subcombination. Similarly, whileoperations are depicted in the drawings in a particular order, thisshould not be understood as requiring that such operations be performedin the particular order shown or in sequential order, or that allillustrated operations be performed, to achieve desirable results.

Moreover, the separation of various system components in the embodimentsdescribed above should not be understood as requiring such separation inall embodiments.

Therefore, it will be appreciated that the scope of the presentapplication fully encompasses other embodiments which may become obviousto those skilled in the art. In the claims, reference to an element inthe singular is not intended to mean “one and only one” unlessexplicitly so stated, but rather “one or more.” All structural andfunctional equivalents to the elements of the above-described preferredembodiment that are known to those of ordinary skill in the art areexpressly incorporated herein by reference and are intended to beencompassed by the present claims. Moreover, it is not necessary for adevice to address each and every problem sought to be solved by thepresent apparatus, systems, and methods, for it to be encompassed by thepresent claims. Furthermore, no element or component in the presentdisclosure is intended to be dedicated to the public regardless ofwhether the element or component is explicitly recited in the claims. Noclaim element herein is to be construed under the provisions of 35U.S.C. 112, sixth paragraph, unless the element is expressly recitedusing the phrase “means for.”

While the apparatus, systems, and methods may be susceptible to variousmodifications and alternative forms, specific embodiments have beenshown by way of example in the drawings and have been described indetail herein. However, it should be understood that the application isnot intended to be limited to the particular forms disclosed. Rather,the application is to cover all modifications, equivalents, andalternatives falling within the spirit and scope of the application asdefined by the following appended claims.

1. An apparatus for thermal environmental control of an optic capable oftransmitting high power fluxes greater than$100\mspace{14mu} \frac{W}{{cm}^{2}}$ such as can be used for thepurposes of additive manufacturing of metal, plastic, or ceramicproducts, comprising: an optic to be thermally managed, a light sourceproducing a high powered light beam that is directed from said lightsource through the optic to be thermally managed, an optic coolingsystem operatively connected to said optic, where the combination ofpressures in the cooling fluid, balanced with temperatures in the opticto be cooled do not result in any significant deformation of the optic,and where the cooling fluid is largely transparent to the high poweredlight beam that is transmitted through the cooling fluid.
 2. Theapparatus for thermal environmental control of an optic of claim 1wherein said light source that produces a light beam is a laser thatproduces a laser beam having energy wherein said energy is transferredto said optic in the form of heat and wherein said optic cooling systemremoves heat from said optic.
 3. The apparatus for thermal environmentalcontrol of an optic of claim 1 wherein said light source that produces alight beam is a diode laser that produces a laser beam having heatwherein said heat is transferred to said optic and wherein said opticcooling system removes heat from said optic.
 4. The apparatus forthermal environmental control of an optic of claim 1 wherein said opticis an optically addressed light valve (OALV) including: a semiconductormaterial transparent to the high power light beam that can be opticallystimulated to induce a change in semiconductor thermal conductivity, alayer of liquid crystal for rotating the polarization state of the highpower light beam as it transmits through the OALV, a substrate materialtransparent to the high power light beam, optically transparentelectrically conductive coatings on the outside of the semiconductor,and between the liquid crystal and the substrate material, andanti-reflective coatings on the two sides of the semiconductor material,and on the two sides of the substrate material.
 5. The apparatus forthermal environmental control of an optic of claim 4 wherein saidsemiconductor material is transparent to 1053 nm light.
 6. The apparatusfor thermal environmental control of an optic of claim 4 wherein saidsubstrate material is transparent to 1053 nm light.
 7. The apparatus forthermal environmental control of an optic of claim 4 wherein said liquidcrystal is of twisted nematic E7.
 8. The apparatus for thermalenvironmental control of an optic of claim 4 wherein said transparentelectrically conductive coatings are Indium Tin Oxide (ITO).
 9. Theapparatus for thermal environmental control of an optic of claim 1wherein said emitted light beam is composed of light in one polarizationstate.
 10. The apparatus for thermal environmental control of an opticof claim 1 wherein said optic is an optically addressed light valve(OALV) including a secondary light source for projecting patterned lightof a wavelength tuned to the absorption band of the semiconductor in theOALV, and a polarizing mirror capable of separating the orthogonalpolarization states induced by polarization rotation of the light beamin the liquid crystal portion of the OALV.
 11. The apparatus for thermalenvironmental control of an optic of claim 1 wherein said optic coolingsystem includes a housing operatively connected to said optic and acooling fluid in said housing.
 12. The apparatus for thermalenvironmental control of an optic of claim 1 wherein said optic coolingsystem includes a housing operatively connected to said optic, a coolingfluid that is circulated in said housing, and a heat exchangeroperatively connected to said cooling fluid.
 13. The apparatus forthermal environmental control of an optic of claim 1 wherein said opticcooling system includes a housing operatively connected to said optic, acooling fluid, a circulation system for circulating said cooling fluidin said housing, a pump operatively connected to said circulationsystem, and a heat exchanger operatively connected to said coolingcirculation system.
 14. A method for thermal environmental control of anoptic capable of transmitting high power fluxes greater than$100\mspace{14mu} \frac{W}{{cm}^{2}}$ used for the purposes ofadditive manufacturing of metal, plastic, or ceramic products,comprising the steps of: enclosing an optic to be cooled in a coolinghousing which allows transmission through the optical system of whichthe optic is a component, flowing a cooling fluid through said coolinghousing, and over the optic to be cooled, where the combination ofpressures in the cooling fluid, balanced with temperatures in the opticto be cooled do not result in deformation of the optic, and where thecooling fluid is transparent to the high powered light beam that istransmitted through the cooling fluid, and illuminating the optic to becooled with a light source producing a high powered light beam that isdirected from said light source through the optic to be thermallymanaged and the optic cooling housing.
 15. The method for thermalenvironmental control of an optic of claim 1 wherein said light sourcethat produces a light beam is a laser that produces a laser beam havingenergy wherein said energy is transferred to said optic in the form ofheat and wherein said optic cooling system removes heat from said optic.16. The method for thermal environmental control of an optic of claim 14wherein said light source that produces a light beam is a diode laserthat produces a laser beam having heat wherein said heat is transferredto said optic and wherein said optic cooling system removes heat fromsaid optic.
 17. The method for thermal environmental control of an opticof claim 14 wherein said optic is an optically addressed light valve(OALV) including: a semiconductor material transparent to the high powerlight beam that can be optically stimulated to induce a change insemiconductor thermal conductivity, a layer of liquid crystal forrotating the polarization state of the high power light beam as ittransmits through the OALV, a substrate material transparent to the highpower light beam, optically transparent electrically conductive coatingson the outside of the semiconductor, and between the liquid crystal andthe substrate material, and anti-reflective coatings on the two sides ofthe semiconductor material, and on the two sides of the substratematerial.
 18. The method for thermal environmental control of an opticof claim 17 wherein said semiconductor material is transparent to 1053nm light.
 19. The method for thermal environmental control of an opticof claim 17 wherein said substrate material is transparent to 1053 nmlight.
 20. The method for thermal environmental control of an optic ofclaim 17 wherein said liquid crystal is of twisted nematic E7.
 21. Themethod for thermal environmental control of an optic of claim 17 whereinsaid optically transparent electrically conductive coatings are ofIndium Tin Oxide (ITO).
 22. The method for thermal environmental controlof an optic of claim 17 wherein said emitted light beam is composed oflight in one polarization state.
 23. The method for thermalenvironmental control of an optic of claim 17 wherein said optic is anoptically addressed light valve (OALV) including: a secondary lightsource for projecting patterned light of a wavelength tuned to theabsorption band of the semiconductor in the OALV, and a polarizingmirror capable of separating the orthogonal polarization states inducedby polarization rotation of the light beam in the liquid crystal portionof the OALV.
 24. The method for thermal environmental control of anoptic of claim 17 wherein said optic cooling system includes a housingoperatively connected to said optic and a cooling fluid in said housing.25. The method for thermal environmental control of an optic of claim 17wherein said optic cooling system includes a housing operativelyconnected to said optic, a cooling fluid that is circulated in saidhousing, and a heat exchanger operatively connected to said coolingfluid.
 26. The method for thermal environmental control of an optic ofclaim 17 wherein said optic cooling system includes a housingoperatively connected to said optic, a cooling fluid, a circulationsystem for circulating said cooling fluid in said housing, a pumpoperatively connected to said circulation system, and a heat exchangeroperatively connected to said cooling circulation system.